In recent years, it has become fashionable to periodically bleach one's teeth in order to accentuate their whiteness. There are various known bleaching compositions that are used for this purpose. In general, the prior art has contemplated the U-shaped trough-like member to hold the bleaching composition in contact with the person's teeth while being bleached.
However, in some cases, the bleaching composition will run out of the rear of the trough-like member, or be displaced upwardly so as to contact a person's gums. In general, it would desirable to retain the bleaching composition in the trough so as to contact a person's teeth, and to prevent such composition from unduly contacting the person's gums.